Apparatus for ultrasonically inspecting a large shaft from a liquid-filled bore

Abstract

 A shipping and storage enclosure for an ultrason­ic inspection system used to inspect turbine and generator rotors from the bore which is flooded with water and which enclosure can be expanded into an operating enclosure in which the environment is controlled to provide for affec­tive operation of the equipment and provide for alignment of the ultrasonic sensing head with the bore of the rotor shaft.

Description

[0001] This invention relates to ultrasonic inspection of steel shafts and more particularly to ultrasonically inspecting large diameter shafts from bores filled with a liquid.

[0002] When ultrasonics are utilized to inspect a large mass of metal, a liquid film is used as a medium to trans­mit ultrasonic sound from the transducer into the metal, however, when only a thin film separates the transducer or sonic lens from the metal, near the surface flaws are often not distinguishable. By moving the transducers a greater distance from the surface, indications of sonic reflections near the surface may become more distinguishable. Since in shafts rotating at high speeds the area adjacent the bore is highly stressed and imperfections in this area will affect the life of the shaft, an inspection system should have good resolution near the bore. This may be accom­plished by moving the transducer away from the bore surface thus improving the near bore resolution of sonic reflectors.

[0003] Large shafts such as are found in turbine and generator rotors are expensive to manufacture and, because of their expense, spare rotors are usually not available. The inspection of such rotors requires a large amount of machinery down-time and, if the rotors must be shipped to a special inspection location, down-time is even greater. A system developed by Southwest Research Institute in joint sponsorship with the Electric Power Research Institute called Turbine Rotor Examination Evaluation System, TREES, uses twelve focus search transducers to determine flaw size. The transducers are utilized in a liquid-filled bore. Although the unit is enclosed in a portable contain­er for easy transportation to field sites, the container is not expandable to provide an enclosed work station at the side of the inspection.

[0004] The primary objective of the present invention is to provide an improved apparatus for ultrasonically in­specting a large bore.

[0005] With that view, the present invention resides in apparatus for ultrasonically inspecting a large shaft from a bore filled with liquid, comprising: a head assembly having at least one transducer disposed thereon for indicating sonic reflectors within the shaft and means for supporting said head concentrically in said bore; a plurality of tubular extensions which fasten to each other and to said head assembly; a cable electrically connected to said transducer and said head assembly and threaded through said tubular extensions; a trough which is partial­ly filled with liquid during the ultrasonic inspection and having mounted on each end thereof means for raising and lowering the trough characterized by a round tube generally the same diameter as said bore mounted in said trough and axially aligned with said bore during the ultrasonic inspection; drive means for moving said tubular extensions and head assembly axially and rotationally; means for producing a signal indicative of the axial and rotational position of said head assembly and transducer; means for providing, receiving and processing ultrasonic and posi­tional signals to operate the apparatus and to produce intelligible information about the location and size of sonic reflectors in said shaft; and an enclosure having floor, wall and roof portions for storing, shipping and operating said elements of said apparatus described herein and controlling the enviroment within said enclosure so that the enviroment is suitable for said apparatus and those who operate it.

[0006] The preferred embodiments of the present inven­tion will be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a sectional view of a shipping, storage and operating enclosure for an ultrasonic inspec­tion apparatus operable in a liquid-filled bore of a large shaft;

Fig 2 is a plan view of an expandable operating enclosure extending from the storage and shipping enclosure;

Fig. 3 is a detailed sectional view of the expanded operating area;

Fig. 4 is an elevational view of a liquid trough which is connected to the bore;

Fig. 5 is a sectional view of the apparatus utilized to position an ultrasonic head in the liquid-filled bore;

Fig. 6 is a sectional view taken on line VI-VI of Fig. 5; and

Fig. 7 is an elevational view of an ultrasonic head disposed in a transparent tube which fits in the trough.

[0007] Referring now to the drawings in detail, there is shown apparatus 1 for ultrasonically inspecting a large shaft 3 from a liquid-filled bore 5.

[0008] The apparatus, as shown in Fig. 1, comprises an expandable, shipping and storage enclosure 6 which, when expanded, provides an enclosed controlled enviroment for operating the ultrasonic inspection equipment. As shown in Fig. 7, the ultrasonic inspection equipment comprises an ultrasonic head 7 having at least one dynamically focused ultrasonic transducer 8 disposed thereon and a plurality of roller feet 9, which are driven outwardly by a motor or other means (not shown) to engage the bore surface and generally support the ultrasonic head 7 so that it is centrally disposed in the bore 5. A plurality of square tubular bars 11 fasten together to move the ultrasonic head 7 in the bore 5. The bars 11 have a gear rack 13 disposed on one side for advancing and retracting the ultrasonic head 7. The square shaped bars are also adapted for turning the ultrasonic head 7 in the bore 5. The opening in the tubular bar 11 provides a cable and tubing run for a cable 15 and tubing (not shown) utilized to connect the ultrasonic head 7 to a computer 17 and to remove air from the bore, respectively.

[0009] In addition to the dynamically focused ultrasonic transducer 8 for detecting sonic reflectors in the shaft, another transducer 19 reflects a signal from an inclined surface 21 to determine the position of the ultrasonic head 7 with respect to the axis of the bore 5.

[0010] To operate the ultrasonic system 1, the computer 17 or other device produces input signals for the transduc­ers 8 and 19 and processes reflected signals received by the transducers 8 and 19. The computer 17 also produces signals to position the ultrasonic head 7 in the bore 5 and processes signals indicative of the position of the ultra­sonic head and the transducer 8 as they progress through the bore 5.

[0011] Since the bore 5 is flooded with liquid during inspection, an elongated trough 23, as shown in Figs. 2, 4 and 6, is partially filled with liquid and is connected to one end of the shaft 3 by a transparent spool piece 25 which has O-ring seals 27 or other sealing means disposed on each end thereof. The shaft 3, bore 5, and trough 23 are inclined so that gas bubbles formed in the bore 5 will come to the surface of the liquid in the trough 23.

[0012] The trough 23 also provides access to the ultra­sonic head 7 and transducers 8 and 19 while they are submerged outside of the bore 5. A calibration block mount 29 is disposed in the end of the trough 23 which is con­nected to the shaft 3 to receive semicircular calibration blocks 31. A pair of rails 33 are disposed in the trough 23 to support a transparent pipe 35 axially aligned with the bore 5 of the shaft 3. When inspecting steam turbine and generator rotor shafts, the largest bores encountered are about 17.8 cm to 19.0 cm in diameter so that the rail is disposed to position a 20.3 cm outside diameter trans­parent pipe such that it is axially aligned with the bore 5. If the bore 5 is smaller in diameter, transparent pipes 35 generally the same inside diameter as the bore 5, are utilized and have collars 37 with an outside diameter of 8 inches spaced at intervals to align the axis of the smaller diameter transparent pipes 35 with the axis of the bore 5.

[0013] Mounted on the end of the trough 23 opposite the shaft 5 is a drive 39, which cooperates with the tubular bars 11 to move the ultrasonic head 7 in axial and rota­tional directions in response to signals from the computer 17. The ultrasonic head then produces signals indicative of its axial and rotational position which are returned to the computer 17.

[0014] The drive 39 comprises an axial drive and signal portion 41 and a rotational drive and signal portion 43. The tubular bars 11 pass through the drive 39 which is enclosed from liquid in the trough by liquid seals 45 disposed adjacent the trough 23. A rotatable support 46 is provided on the other end of the drive 39.

[0015] The trough 23 and drive 39 for the tubular bars 11 are mounted on an I-beam 47 which provides a rigid base to maintain alignment of the guide rails 33, drive 39 and calibration block 29 once proper alignment has been achieved. The I-beam 47 is mounted on adjustable legs 49 which allow the trough to be inclined to align it with the inclined shaft 3. Besides being movable vertically, the legs 49 can also be moved sideways to align the trough with the shaft. One set of legs 49 also slides back and forth as the inclination of the trough 23 is altered to conform with shaft alignment. Alignment should be within ±0.25 cm and may be performed utilizing a builders level, the tight wire method or a laser alignment system.

[0016] A track 51 extends from the end of the I-beam 47 opposite the shaft 3 and has a carriage 53 which runs thereon. A support 55 with an opening for receiving the tubular bar 11 is disposed on one end of the carriage 53 and an elongated support 57 is disposed on the other end of the carriage 53 for receiving the tubular bar 11 or the cable 14 to support the portion of the tubular 11 and cable 15 extending beyond the drive 39. The computer 17, trough 23, ultrasonic head 7 and all the support equipment associated with the operation is mounted, installed, stored, transported in and operated from the enclosure 6 which can be transported by truck, aircraft or sea-going vessel with adequate provisions for protecting the sensi­tive equipment.

[0017] The enclosure 6 has an outside dimension approxi­mately 2.4 m × 2.6 m × 6.1 m and is built like an enclosed truck body without wheels except that all eight corners have standard lifting or tie-down lugs 63 attached to a reinforced frame structure within the enclosure 6.

[0018] The enclosure 6 has a floor 65, walls 67 and a roof and ceiling 69. There are two doors, an entrance door 71 and a double door 73, which opens one end of the enclo­sure 6. Mounted on and extending through the roof and ceiling 69 are two air-conditioning units 75 to control the temperature in the enclosure 6 for the efficient operation of the equipment and the people operating it. The enclo­sure 6 is provided with a transformer with variable taps so that a single high-voltage line can be hooked up to the transformer and the voltage reduced to various levels to provide the proper power for the air-conditioner 75, computer 17, motors, lighting and other electrical requirements.

[0019] Behind the double doors 73 on one end of the enclosure 6 is an expandable portion which comprises a floor portion 77 which folds up into the end of the enclo­sure 6; is hinged at the floor 65; and has a hinge 79 disposed in the middle which generally rotates 180° so that the floor portions 77 also fold on themselves, thus provid­ing a floor extension which is generally twice as long as the walls 67 are high. A pair of cables 81 are connected between the upper portion of the walls 67 and the outer portion of a frame support 83, which helps support the extended floor portion 77. The frame support 83 fits under the extended floor portion 77 and attaches to the enclosure 6 to provide further support for the extended floor portion 77. The frame support 83 is formed from aluminum channels and can be disassembled and stored in the enclosure 6 when the equipment is prepared for storage and shipment.

[0020] A fabric tent-like portion 85 extends from and is connected from the ceiling 69, walls 67, and tubular supports 87 connected to the floor extension 77 to form a frame over which the fabric tent-like portion 85 is stretched. This substantially increases the enclosed area and provides additional work area within a controlled enviroment from which to operate the apparatus.

[0021] The computer 17 is mounted in the enclosure 6 with shock-absorbing mounts 89 to protect it during storage and when in transit.

[0022] The cable 15 is continuous and connects the ultrasonic head 7 and transducers 8 and 19 to the computer 17 and is threaded serially through the tubular bars 11. When the apparatus is in storage or in shipment, the tubular bars with the cable 15 extending therethrough are stored in a rack 91. As shown in Figs. 5 and 6, the rack 91 comprises a plurality of the sheet metal carriages 93 which provide means for holding one or more tubular bars 11 and which are removably fastened to a slidable base portion 94 which allows the tubular bars 11 to be stored in the enclosure 6 above the trough 23 and to slide out into the expanded enclosure during operation of the ultrasonic equipment.

[0023] The carriage 93 is removed from the rack 91 with the tubular bars 11 and cable 15 in place thereon. The carriage 93 is then hooked on brackets on the tubular supports 87 for the tent-like structure 85, thus improving the positioning before the tubular bars 11 are serially attached to the ultrasonic head 7.

[0024] Work stations 95 for operating the computer 17 are disposed in the enclosure 6 opposite the trough 23.

[0025] An I-beam 97 is pivotally mounted in the corner of the enclosure 61 adjacent the end of the trough 23 which has the calibration block mount 29. A trolley 99 rolls on the I-beam 97 and has an attached hoist 101 to install and remove the calibration blocks 31 from the trough 23. The calibration blocks 31 are stored on dollies 103 to which they are fastened during storage and shipment. The dollies 103 have bolts or other means for fastening them to the floor 69 so that they will not move during storage or shipment. However, the dollies provide easy access to the calibration blocks during the operation of the equipment even though the calibration blocks weigh hundreds of pounds.

[0026] In the enclosure is also a water treatment system 105 which filters and deaerates the water or other liquid utilized to fill the shaft and trough.

Claims

1. Apparatus for ultrasonically inspecting a large shaft from a bore filled with liquid, comprising:
    a head assembly having at least one transducer disposed thereon for indicating sonic reflectors within the shaft and means for supporting said head concentrically in said bore;
    a plurality of tubular extensions which fasten to each other and to said head assembly;
    a cable electrically connected to said transducer and said head assembly and threaded through said tubular extensions;
    a trough which is partially filled with liquid during the ultrasonic inspection and having mounted on each end thereof means for raising and lowering the trough characterized by
    a round tube generally the same diameter as said bore mounted in said trough and axially aligned with said bore during the ultrasonic inspection;
    drive means for moving said tubular extensions and head assembly axially and rotationally;
    means for producing a signal indicative of the axial and rotational position of said head assembly and transducer;
    means for providing, receiving and processing ultrasonic and positional signals to operate the apparatus and to produce intelligible information about the location and size of sonic reflectors in said shaft; and
    an enclosure having floor, wall and roof portions for storing, shipping and operating said elements of said apparatus described herein and controlling the environment within said enclosure so that the enviroment is suitable for said apparatus and those who operate it.

2. Apparatus as set forth in claim 1 further characterized by the enclosure having one end wall position which is expandable to substantially increase the enclosed work area an which can be placed back in the original enclosure for storage and shipment.

3. Apparatus as set forth in claim 2 further characterized by the expandable end of the enclosure comprising a floor portion which folds up into the one end of the enclosure for shipping and storage.

4. Apparatus as set forth in claim 3 further characterized by the expandable floor portion being hinged in the middle whereby the extended floor area is generally twice as long as the enclosure wall portions are high.

5. Apparatus as set forth in claim 4 further characterized by the middle hinge only rotating 180°.

6. Apparatus as set forth in claim 5 further characterized by a pair of cables connected to the upper portion of the walls of the enclosure and the outer portion of the extended floor portion.

7. Apparatus as set forth in claim 3 further characterized by a fabric member extending from and con­nected to the roof and side walls of the enclosure and supports connected to the extended floor, the fabric member extending over the supports to form a roof and side walls for the extended work area.

8. Apparatus as set forth in claim 1 further characterized by the cable being continuous.

9. Apparatus as set forth in claim 1 further characterized by the trough and shaft being inclined during operation to assist in removing air bubbles from the liquid in the bore.

10. Apparatus as set forth in claim 1 further characterized by the trough having means for mounting a calibration block disposed in one end thereof.

11. Apparatus as set forth in claim 10 further characterized by a calibration block having a cylindrical portion generally the same diameter as the bore and being disposed in the trough.

12. Apparatus as set forth in claim 10 further characterized by the end of the trough with the calibration block disposed therein being adjacent one end of the enclosure and having sealing means cooperatively associated therewith for connecting the bore of the shaft to the trough and forming a fluid seal therebetween.

13. Apparatus as set forth in claim 12 further characterized by a carriage disposed adjacent the other end of the trough for supporting portions of the tubular extension before said portions enter the trough and bore.

14. Apparatus as set forth in claim 8 further characterized by means of storing said tubular extensions with the cable extending therethrough in such a manner that said extensions can be readily connected in series to extend the head assembly deeper into the bore.

15. Apparatus as set forth in claim 10 further characterized by means for installing and removing calibra­tion blocks from the trough and means for storing the calibration blocks.

16. Apparatus as set forth in claim 15 further characterized by the means for installing and removing and storing the calibration blocks includes a beam connected to the enclosure, a trolley which runs on said beam, a hoist connected to said trolley for installing and removing the calibration blocks and a dolly on which the calibration blocks may be placed during storage and shipment.

17. Apparatus as set forth in claim 1 further characterized by the means for producing, receiving and processing said signals being mounted in the enclosure with shock mounts so that it will not be damaged during storage or shipment.

18. Apparatus as set forth in claim 1 further characterized by the round tubes being made of transparent material so that the head assembly can be observed in the trough.

19. Apparatus as set forth in claim 12 further characterized by the seal means comprising a spool piece with a gasket on each end thereof.

20. Apparatus as set forth in claim 19 further characterized by at least the center portion of the spool piece being made of transparent material.

Drawing